1. Field of the Invention
The present invention relates to a laser machining method and a laser machining apparatus, and more particularly to a laser machining method and a laser machining apparatus by which a fine pattern can be formed on a material at high speed.
2. Description of the Related Art
A variety of materials have been heretofore worked in accordance with wet etching method wherein various chemical solutions are used, or laser ablation method wherein various types of laser are used.
However, it has been known that among a variety of materials, for example, quartz glass has an absorption edge of light of around 170 nm, besides bond energy between constituent atoms is also remarkable, so that it is difficult to form a fine pattern on a material at high speed in accordance with such a conventional machining method as described above.
More specifically, when quartz glass is worked up according to wet etching method wherein a chemical solution such as acid is used, a speed in working is fast, but there has been a problem of poor controllability for working profile and working speed of the quartz glass, so that the method is not suitable for fine working.
Furthermore, although reactive ion etching method (RIE) is a machining method suitable for effecting precisely fine working of quartz glass, there has been a problem of slow working speed (It is known to be a working speed of 1 nm/s or less in case of working SiO2).
Moreover, there has been such a problem that another lithographic step using a resist is necessary for effecting fine pattern working in wet etching method wherein the above described chemical solution such as acid is employed or reactive ion etching method, so that the whole steps for working treatment become complicated, resulting in a reason of requiring a long period of time.
On the other hand, there is laser ablation method as a method for pattern-working a material at high speed without employing a resist, but it is necessary that a wavelength of laser beam applied in laser ablation method has a high absorption coefficient with respect to a material to be worked. For this reason, when quartz glass is intended to work in accordance with laser ablation method, it is required to use laser beam having a wavelength of 170 nm or less. In this connection, however, there has been such a problem that a laser applicable for working of quartz glass is not substantially present with taking costs for photon, and output thereof into consideration.